<!DOCTYPE html>
<html lang="en">

<head>
    <meta charset="UTF-8">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>Document</title>
</head>

<body>

    <header>
        我是header
    </header>

    <main>

        <aside>
            我是aside
        </aside>
        我是main
    </main>
    <div id="demo">11</div>
    <footer> 我是footer</footer>

</body>

<script>
    /* 常用的鼠标类型:
        onclick     鼠标左键点击触发
        ondblclick  鼠标左键双击触发
        onmousedown 鼠标按键按下触发
        onmouseup   鼠标按键放开时触发
        onmousemovwe鼠标在元素上移动触发
        onmouseover 鼠标移动到元素上触发
        onmouseout  鼠标移出元素边界触发
         */
    let btn = document.getElementById("demo")
    btn.onclick = () => {
        alert("d")
    }
</script>

</html>